1. Field of the Invention
The present invention relates to a printed wiring board such as a package substrate to mount electronic components such as an IC.
2. Discussion of the Background
FIG. 11 shows a printed wiring board which structures a package substrate relating to background art. In printed wiring board 210, to mount IC chip 290 on the substrate, multiple solder bumps 276 are formed on the substrate, and solder-resist layer 270 is formed. Conductive circuit 258 including solder pads 275 is formed on the substrate, and solder-resist layer 270 is formed to coat conductive circuit 258. Openings 271 corresponding to the solder pads are formed in solder-resist layer 270, and then on the surfaces of solder pads 275 exposed through openings 271, a nickel-plated layer and a gold-plated layer (those two layers are indicated by numerical reference 274) are formed. Underfill (resin for sealing) 288 is filled between IC chip 290 and the substrate.